In vitro diagnostics (IVD) allows labs to assist in the diagnosis of disease based on assays performed on patient fluid samples. IVD includes various types of analytical tests and assays related to patient diagnosis and therapy that can be performed by analysis of a liquid sample taken from a patient's bodily fluids, or abscesses. These assays are typically conducted with automated clinical chemistry analyzers (analyzers) onto which fluid containers, such as tubes or vials containing patient samples have been loaded. The analyzer extracts a liquid sample from the vial and combines the sample with various reagents in special reaction cuvettes or tubes (referred to generally as reaction vessels). In some prior art systems, a modular approach is used for analyzers. A lab automation system can shuttle samples between one modular testing station (e.g., a unit that can specialize in certain types of assays or can otherwise provide testing services to a larger analyzer) and another. This allows different types of tests to be specialized in two different stations or allows two redundant stations to be linked to increase the volume of sample throughput available. These lab automation systems, however, are often bottlenecks in multi-station analyzers. Relatively speaking, traditional lab automation systems lack large degrees of intelligence or autonomy to allow samples to independently move between stations.
In an exemplary prior art system, a friction track, much like a conveyor belt, shuttles individual carrier mechanisms, sometimes called pucks, or racks of containers between different stations. Samples may be stored in sample containers, such as test tubes that are placed into a puck by an operator or robot arm for transport between stations in an analyzer along the track. This friction track, however, can only move in one direction at a time and any samples on the track will move in the same direction at the same speed. When a sample needs to exit the friction track, gating/switching can be used to move individual pucks into offshoot paths (sometimes called sidecars or pullouts). A drawback with this configuration is that singulation, which is often slow, must be used to control the direction of any given puck at each gate and switch. For example, if two pucks are near one another and only one puck should be redirected into an offshoot path, it becomes difficult to control a switch so that only one puck is moved into the offshoot path and ensure that the proper puck is pulled from the friction track. This has created the need in many prior art systems to have pucks stop at a gate so that individual pucks can be released and switched one at a time at each decision point on a track.
Another way that singulation has been used in friction track-based systems is to stop the puck at a gate and allow a barcode reader to read a barcode on the sample tube. Because barcode readers are slow relative to the amount of time needed to switch a puck between tracks, scanning introduces hard singulations into the flow on a track and causes all nearby pucks to halt while a switching determination is made. After a determination is made, singulation may be further used to ensure that only the scanned puck proceeds by using a physical blockage to prevent the puck behind the scanned puck from proceeding, while the scanned puck is switched.
U.S. Pat. No. 6,202,829 shows an exemplary prior art friction track system that includes actuated mechanical diversion gates that can be used to direct pucks off of the main track onto pullout tracks. As explained therein, the diversion process can require multiple mechanical gates to singulate and separate individual pucks, stopping each puck multiple times and allowing each puck to be rotated so that a barcode can be read before a diversion decision is made. Such a system increases latency and virtually ensures that each time a diversion gate is added to a friction track, the gate adds another traffic bottleneck. Such a system results in natural queuing at each diversion gate, further increasing the amount of time that each sample spends on the friction track.
While there has been some development of autonomous transport carriers outside the IVD environment, such as industrial and shipping environments, there has yet to be an effective system that uses independently routable and positionable carriers in an IVD setting. One reason for the lack of automated carriers may include the need for precise positioning of vessels holding samples or reagents in relation to stations, such as testing stations or other sample handling stations. For example, a carrier must be able to reliably position itself at a destination to within about a centimeter to allow aspiration of the sample carried. Similarly, the small size needed for carriers in an IVD setting and relatively small size of features of tracks used to transport samples present challenges in adapting systems and techniques used in industrial systems. Furthermore, in an IVD environment, automation systems have traditionally favored reliability over complexity, favoring passive carriers, rather than the added complexity of active carriers.